The present invention relates to a new and improved construction of an apparatus for placing flat cover elements, preferably cover sheets, on stacks of flat articles, preferably printed products.
In its more particular aspects, the present invention specifically relates to a new and improved apparatus for placing flat cover elements, preferably cover sheets, onto stacks of flat articles, preferably printed products, and which contains a placing element which is displacable between an upper standby or preparatory position and a lower operative position for displacing the cover elements or sheets from a waiting position onto one of the stacks. The one stack is movable along a predetermined conveying path past the placing or placement element. The apparatus further possesses a control means or arrangement for controlling the movement or displacement of the placing element which, on arrival of a stack, triggers a displacement of the placing element towards its operative position and, after placing the cover element onto the stack, effects a return movement of the placing element towards its standby or preparatory position.
In an apparatus of this type as known, for example, from Swiss Pat. No. 545,741, granted Dec. 31, 1973, the stacks or paper stacks which are to be provided with a cover sheet, are moved with constant speed past a cover element or sheet placing station by means of a conveyor belt. At this placing station a cover element or sheet is placed onto the passing stack without the stacks having to be stopped for this purpose. The placing of the cover elements or sheets occurs with the assistance of a placing element or ram which can be raised or lowered in a direction which extends at right angles to the conveying direction of the stack. In a preparatory position of the ram the latter entrains a cover element or sheet and places this cover element or sheet in the operative position upon the associated stack. In order to ensure that the ram including the cover element or sheet comes to rest upon the stack independent of the height of the stack, when the stack is aligned with the movement axis of the ram, relatively complicated control means including a light barrier are provided. Depending upon the height of the next arriving stack, the light barrier triggers the downward movement of the ram either at an earlier or later moment of time.
By means of a further control arrangement which also possesses a light barrier, the arrival of the ram at the operative position is detected and the return movement into the standby or preparatory position is initiated.
This known apparatus does have the advantage that the movement of the stack does not have to be interrupted for placing the cover elements or sheets, that is the stack does not have to be briefly stopped and thereafter accelerated again. For this purpose, however, a relatively large expense in terms of apparatus and control techniques is necessary.